HPLC is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2026-03-16. Numbers and descriptions here follow the published literature rather than marketing material.
Several separation modes exist, including reversed-phase, normal-phase, ion-exchange, size-exclusion, and hydrophilic interaction liquid chromatography. Reversed-phase uses a nonpolar stationary phase with a polar mobile phase and is widely applied to small organic molecules. Gradient elution changes mobile phase composition during the run, while isocratic elution keeps it constant. Column chemistry, particle size, temperature, flow rate, and mobile phase pH all influence retention and resolution. Method development selects conditions that separate analytes from matrix components and from each other.
Detection commonly uses ultraviolet-visible absorbance, fluorescence, refractive index, or mass spectrometry. Ultraviolet detection depends on molecular chromophores that absorb light at specific wavelengths. Mass spectrometry provides mass information and sensitive quantification, often after electrospray ionization. Before sample batches, performance checks examine resolution, elution time repeatability, peak symmetry, and plate count. Matrix effects and co-elution remain recognized uncertainties; formal validation studies and orthogonal detection help address them. Detector choice depends on analyte properties and required sensitivity.
High-performance liquid chromatography, or HPLC, separates dissolved compounds by passing a liquid mobile phase through a packed column. Components distribute differently between the stationary phase and the moving liquid, so they travel at different speeds and exit at different times. A detector records these eluting bands as peaks, and peak area or height relates to amount. The technique supports testing in pharmaceuticals, foods, environmental samples, and industrial chemicals. Quantification usually depends on calibration with known standards.
High-performance liquid chromatography is an analytical technique that separates components in a liquid sample. A pump moves a liquid mobile phase through a column packed with a solid stationary phase. Compounds interact differently with both phases and travel at different rates, leaving the column at distinct retention times. A detector records these arrivals as peaks on a chromatogram. The resulting pattern supports identification and quantification of substances in mixtures. Modern instruments use high pressure to force solvent through small particles, which improves speed and resolution compared with older low-pressure liquid chromatography methods.
Separation in HPLC depends on the chemistry of the stationary phase, the composition of the mobile phase, and the physical properties of the column. Reverse-phase separations use a nonpolar stationary phase and a polar mobile phase, and they are common for many organic compounds. Ion-exchange, size-exclusion, and normal-phase modes serve other classes of analytes. Gradient elution changes solvent strength over time, while isocratic elution holds it constant. Flow rate, temperature, particle size, and column length all influence peak shape and resolution. Detection may use ultraviolet absorbance, fluorescence, refractive index, or mass spectrometry, depending on the analyte and the required sensitivity.
| Property | Value | Notes |
|---|---|---|
| Column particle size | 3–5 µm for conventional HPLC; sub-2 µm for UHPLC | Smaller particles increase backpressure and efficiency. |
| Typical flow rate | 0.5–2.0 mL/min for a 4.6 mm internal diameter column | Flow scales with column diameter and particle size. |
| UV detection wavelength | 190–400 nm | Selection depends on analyte chromophore. |
| Column temperature | 25–40 °C | Temperature affects retention, selectivity, and pressure. |
| Injection volume | 1–20 µL | Larger volumes may distort early-eluting peaks. |
System suitability testing is performed before and during analytical runs to confirm that the instrument and method are working as expected. Typical checks include retention time, peak area precision, resolution between critical pairs, tailing factor, and theoretical plate count. Acceptance criteria are set in the method or pharmacopeial monograph. If a suitability check fails, the run may be rejected and the instrument or sample preparation may need investigation. This practice helps prevent release of data from a system that has drifted out of control.
Quality control samples are inserted at intervals to monitor accuracy and precision throughout a batch. Blank samples detect contamination, while spiked samples assess recovery from the sample matrix. Calibration standards establish the relationship between detector response and concentration, and control samples are prepared independently from them whenever possible. Laboratories also participate in proficiency testing and maintain audit trails, instrument logs, and reagent records. Ongoing review of control charts can reveal trends before they cause out-of-specification results.
Method validation demonstrates that an HPLC procedure is suitable for its intended purpose. Common validation parameters include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantification, and robustness. Accuracy reflects agreement with a reference value, while precision describes repeatability under defined conditions. Specificity shows whether the method can measure the analyte in the presence of impurities or matrix components. Validation documents are reviewed before a method is used for routine testing or regulatory submissions.
Method validation establishes that an HPLC procedure is suitable for its intended use. Key parameters include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantitation, and robustness. Accuracy measures agreement with a true or accepted value, while precision describes repeatability and intermediate precision. Specificity confirms that the method measures the analyte without interference from impurities, degradants, or excipients. Validation is documented in a protocol and report, and acceptance criteria are set before experiments begin. Regulatory guidance varies by region, but the general principles are widely harmonized.
System suitability testing is performed before and during analytical runs to confirm that the instrument and method are working as expected. Common checks include retention time, peak area, resolution between critical pairs, tailing factor, and theoretical plate count. Results are compared with predefined limits, and a failed check requires investigation before sample results are reported. Quality control samples at low, middle, and high concentrations are injected at intervals to monitor accuracy and precision. Blank injections detect carryover and contamination, while control charts track performance over time.
Data handling and documentation are central to HPLC quality control. Electronic systems should have audit trails that record changes to methods, sequences, and results. Integration parameters, such as peak baseline and threshold, can affect reported areas and must be defined in advance. Out-of-specification results trigger a structured investigation that may include reanalysis, instrument checks, and review of sample preparation. Regulatory inspections often examine raw data, audit trails, and training records to verify that reported results are traceable and reliable.
Instrumentation includes a solvent delivery system, an autosampler, a column oven, and one or more detectors. Reversed-phase columns with chemically modified silica are widely used, but normal-phase, ion-exchange, size-exclusion, and affinity modes exist for specific separations. Detectors may rely on ultraviolet absorbance, fluorescence, refractive index, or mass spectrometry. Column temperature, mobile phase composition, and flow rate are adjusted to improve resolution. System pressure is monitored because rising pressure can indicate column blockage or deteriorating packing.
Separation performance depends on particle size, pore size, column length, and the chemistry of the stationary phase. Smaller particles generally improve efficiency but require higher pressure and suitable instrumentation. The mobile phase often contains buffers and organic solvents that influence retention and selectivity. Testing labs select conditions based on the analytes, sample matrix, and required sensitivity. Method development frequently involves screening several columns and solvent mixtures before a final set of conditions is chosen.
High-performance liquid chromatography is an analytical technique that separates components in a liquid sample by passing them through a packed column under pressure. A pump delivers a mobile phase at a controlled flow rate, and an injector introduces the sample into the stream. Differences in how analytes partition between the mobile phase and the stationary phase cause them to exit the column at different times. Detection then records a signal proportional to the amount of each separated substance. The resulting chromatogram provides retention times and peak areas for identification and quantification.
Detection in HPLC testing commonly relies on ultraviolet-visible absorbance, fluorescence, refractive index, or mass spectrometry. A diode array detector records full spectra across a wavelength range, which helps identify co-eluting peaks. Mass spectrometry provides mass-to-charge ratios and can confirm molecular identity at low concentrations. The choice of detector depends on analyte structure, required sensitivity, and whether quantitation or identification is the goal. No single detector works for every compound, and method development often compares responses before selecting one.
High-performance liquid chromatography is an analytical technique that separates components of a liquid sample by passing it through a packed column under pressure. A pump delivers a mobile phase at a controlled flow rate, and an injector introduces the sample into the stream. Differences in interaction with the stationary phase cause analytes to migrate at different rates. Detectors record elution as peaks, and a data system converts signals into a chromatogram. The method is suited to compounds that dissolve in a liquid and are not volatile enough for gas chromatography.
Reversed-phase chromatography dominates modern HPLC testing, using a nonpolar stationary phase such as chemically bonded octadecyl groups and a polar mobile phase of water mixed with organic solvent. Analytes partition between the mobile and stationary phases according to hydrophobicity. Gradient elution changes the mobile phase composition over time to separate compounds with a wide range of retention. Isocratic elution keeps the composition constant and is simpler for routine assays. Column temperature, pH, and flow rate influence selectivity, peak shape, and retention time, so these parameters are controlled during a validated method.
During the period he was Labour MP for Glasgow Kelvin, from 1997 to 2003, he voted against the whip 32 times, five votes out of 665 (0.8%) in the 1997–2001 parliament and the majority (27 votes out of 209 or 12.9%) in the period from the 2001 election until his expulsion from the Labour Party. He was one of several politicians arrested in February 2001 during a protest at the Faslane nuclear base in Scotland, which led to him being convicted of a breach of the peace and fined £180. In May 2002, he was among the 72 MPs who signed The Guardian's campaign to repeal the Act of Settlement 1701, alongside the Archbishop of York David Hope and several non-Anglican religious leaders.
In the 2018 legislative and municipal elections, where Bukele was favored to win re-election before his expulsion, the FMLN had its worst performance since 1994, the party's first election. It lost six seats in the Legislative Assembly, and 16 municipalities. During the election, Bukele called on his supporters nationwide to spoil their vote or stay home on election day rather than support the FMLN. In February 2019, FMLN presidential communications secretary Roberto Lorenzana stated that Bukele's expulsion was a mistake that cost the party votes. In 2025, Bukele remarked that he was "mistaken" ("equivocado") for having previously voted for the FMLN.
March 5 Trump appoints DHS Secretary Noem as the "Special Envoy for The Shield of the Americas," a security initiative focusing on the Western Hemisphere. Trump nominates U.S. Senator Markwayne Mullin to replace Noem as DHS Secretary. The Pentagon officially designates artificial intelligence company Anthropic a supply chain risk – the first time the government has given this label to a domestic firm. Anthropic states it will challenge the decision in court. March 6 – Virginia passes legislation to prohibit schools from teaching about falsehoods of the January 6 United States Capitol attack. March 7 – Trump hosts the first Shield of the Americas summit in Doral, Florida, with 12 Latin American countries in attendance. Mach 10 – U.S. federal judge Sarah D. Morrison rules that the prediction market Kalshi constitutes as gambling and must adhere to state gambling regulations. March 11 – 2026 Minab school attack: A preliminary inquiry finds that the U.S. is at fault for an airstrike which killed 168–180 people at a girls' only elementary school in Minab, Iran. March 12 Temple Israel synagogue attack: A suspected attacker is killed after a vehicle rams into a synagogue in West Bloomfield, Michigan, and travels "with purpose down the hall of the building". 2026 Old Dominion University shooting: A former National Guardsman opens fire at an ROTC class at Old Dominion University in Norfolk, Virginia, killing the instructor and injuring two cadets. Cadets subdue the shooter, with one fatally stabbing him.
Sources: en.wikipedia.org
The CAMP test (Christie–Atkins–Munch-Petersen) is a test to identify group B β-hemolytic streptococci (Streptococcus agalactiae) based on their formation of a substance, CAMP factor, that enlarges the area of hemolysis formed by the β-hemolysin elaborated from Staphylococcus aureus. Although the test is usually used to identify group B streptococcus, there is some evidence that the CAMP factor gene is present in several groups of streptococci, including group A. CAMP factor is a phospholipase produced by Group B Streptococci (Streptococcus agalactiae) that enhances hemolysis of Staphylococcus aureus. A similar factor has been identified in Bartonella henselae. The CAMP test can be used to identify Streptococcus agalactiae. Though not strongly beta-hemolytic on its own, group B strep presents with wedge-shaped colonies in the presence of Staphylococcus aureus. It can also be used to identify Listeria monocytogenes which produces a positive CAMP reaction.
Nobelium is a synthetic chemical element; it has symbol No and atomic number 102. It is named after Alfred Nobel, the inventor of dynamite and benefactor of science. A radioactive metal, it is the tenth transuranium element, the second transfermium, and is the fourteenth member of the actinide series. Like all elements with atomic number over 100, nobelium can only be produced in particle accelerators by bombarding lighter elements with charged particles. A total of twelve nobelium isotopes are known to exist; the most stable is 259No with a half-life of 58 minutes, but the shorter-lived 255No (half-life 3.1 minutes) is most commonly used in chemistry because it can be produced on a larger scale. Chemistry experiments have confirmed that nobelium behaves as a heavier homolog to ytterbium in the periodic table. The chemical properties of nobelium are not completely known: they are mostly only known in aqueous solution. Before nobelium's discovery, it was predicted that it would show a stable +2 oxidation state as well as the +3 state characteristic of the other actinides; these predictions were later confirmed, as the +2 state is much more stable than the +3 state in aqueous solution and it is difficult to keep nobelium in the +3 state. In the 1950s and 1960s, many claims of the discovery of nobelium were made from laboratories in Sweden, the Soviet Union, and the United States. Although the Swedish scientists soon retracted their claims, the priority of the discovery and therefore the naming of the element was disputed between Soviet and American scientists.
=== November === 1 November Amid an ongoing boom in artificial intelligence, the UK hosts the world's first international summit devoted to safely managing the technology. Computer simulations reveal that remnants of a protoplanet named Theia could be inside the Earth, left over from a giant collision in ancient times, which afterwards formed the Moon. Dinkinesh, previously thought to be a single asteroid, is revealed by NASA's Lucy probe to in fact be a binary pair. 5 November – A new record high efficiency of 33.9% is reported for a silicon-perovskite tandem solar cell. This also surpasses the Shockley-Quieser theoretical limit of 33.7% of single junction solar cells for the first time. 6 November – Scientists release the first connectome of neuropeptide signaling in an animal nervous system (C. elegans). On 1 November, a functional atlas of signal propagation in 23,433 pairs of neurons across the worm's head by direct optogenetic activation is published. On 17 November, the development of fluorescent neuropeptide sensors is reported. 7 November – A study finds that "catastrophic ecosystem collapse" of UK forests is likely within the next 50 years, due to a wide range of factors. 8 November – In 10 studies, researchers of the Sc2.0 project report yeast with a half-synthetic genome. 9 November – Surgeons report the first human eye transplant; the patient did not regain sight in the transplanted eye. 10 November – A new scalable technique for carbon nanotube-based MOSFETs is demonstrated.
==== Gekkota (Gekkos) ==== Clade Gekkomorpha Family Eublepharidae Eublepharis macularius, Leopard gecko (2016) Family Gekkonidae Lepidodactylus listeri, Lister's gecko (2025) Family Diplodactylidae Correlophus ciliatus, crested gecko (2024)
Sources: en.wikipedia.org
=== Detection in biological fluids === U-47700 may be measured in serum, plasma, blood or urine to monitor for abuse, confirm a diagnosis of poisoning, or assist in a medicolegal death investigation. Serum or blood U-47700 concentrations are expected to be in a range of 10–250 μg/L in intoxicated patients and 100–1,500 μg/L in deceased victims of acute overdosage. The detection usually involves analysis by liquid chromatography-mass spectrometry.
is the fraction of receptor bound by the ligand. This expression is one way to consider the effect of a drug, in which the response is related to the fraction of bound receptors (see: Hill equation). The fraction of bound receptors is known as occupancy. The relationship between occupancy and pharmacological response is usually non-linear. This explains the so-called receptor reserve phenomenon i.e. the concentration producing 50% occupancy is typically higher than the concentration producing 50% of maximum response. More precisely, receptor reserve refers to a phenomenon whereby stimulation of only a fraction of the whole receptor population apparently elicits the maximal effect achievable in a particular tissue. The simplest interpretation of receptor reserve is that it is a model that states there are excess receptors on the cell surface than what is necessary for full effect. Taking a more sophisticated approach, receptor reserve is an integrative measure of the response-inducing capacity of an agonist (in some receptor models it is termed intrinsic efficacy or intrinsic activity) and of the signal amplification capacity of the corresponding receptor (and its downstream signaling pathways). Thus, the existence (and magnitude) of receptor reserve depends on the agonist (efficacy), tissue (signal amplification ability) and measured effect (pathways activated to cause signal amplification). As receptor reserve is very sensitive to agonist's intrinsic efficacy, it is usually defined only for full (high-efficacy) agonists.
== Consumers and safety == Umami is used as a flavor by food manufacturers trying to improve the taste of low sodium offerings. Incorporating umami into foods can reduce the reliance on salt, as umami enhances the perception of saltiness without diminishing overall flavor. Umami may account for the long-term formulation and popularity of ketchup. The United States Food and Drug Administration has designated the umami enhancer monosodium glutamate (MSG) as a safe ingredient. While some people identify themselves as sensitive to MSG, a study commissioned by the FDA was only able to identify transient, mild symptoms in a few of the subjects, and only when the MSG was consumed in unrealistically large quantities. There is also no apparent difference in sensitivity to umami when comparing Japanese and Americans.
Sources: en.wikipedia.org
HPLC separates and quantifies compounds in a liquid sample. Detectors produce a response proportional to the amount of a compound passing through the flow cell. Identification by retention time requires comparison with a known standard.
UHPLC uses columns with smaller particles and operates at higher pressures than conventional HPLC. These conditions can improve speed, resolution, and sensitivity. Both techniques use the same fundamental separation principles.
Validation shows that a method performs reliably for its intended purpose across a defined range. It assesses accuracy, precision, specificity, linearity, and robustness. Regulated testing often requires documented validation before routine use.
HPLC testing measures the presence and amount of one or more compounds in a liquid sample. It separates mixture components and records detector responses as peaks, which are compared with reference standards. Results are usually reported as concentrations or relative percentages.